Such a device is disclosed in U.S. Pat. No. 4,736,826. This publication describes a mobile robot remotely powered through an electric cord from a stationary console. The robot carries a cord managing arrangement which stores the cord and pays out or retracts the cord as needed. The arrangement lays down the cord under zero tension when the robot is outbound and reels it in as the robot returns. Thereby, the robot can follow a tortuous path without entangling the cord under or around obstacles. The cord is stored on the cord winding reel and is engaged by the drive element, which is a rotating sheave having a groove. The cord is pressed into the groove by a rotating member, so that friction between the cord and the sheave is generated. A first electric motor drives the sheave in order to pay out the cord, whereby the cord is unwound from the reel. As a result, the reel is driven by a second electric motor in a cooperative manner in order to facilitate an appropriate supply of cord to the rotating sheave. When retracting the cord, the second motor drives the reel such that the cord is stored on the reel, while said first motor drives the rotating sheave in a cooperative manner so that the cord is gathered into a tight bundle on the reel.
Such a cord paying out and retracting device can be used for many purposes, for example for paying out and retracting the electric power cord of a robotic vacuum cleaner when the vacuum cleaner is traveling during its cleaning action. It is required for the cord to be paid out and retracted along with the traveling speed of the vacuum cleaner in a controlled manner. The traveling speed of the vacuum cleaner can be measured or calculated, and the paying out or retracting speed of the cord can be adapted to this speed by control means.